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91 crx p28 hondata ecu no power - main relay good!

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Old May 24, 2020 | 09:51 AM
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Default SOLVED - 91 crx p28 hondata ecu no power - main relay good!

P28 with hondata shut off while driving and no power to ecu now. I know my ECU has no power because I cannot see any lights on my hondata and it stopped communicating with my computer. I have gone through replacing all ecu capacitors and renewing thermostat and transmission ground wires. I also tested and re soldered my main relay just to be sure. I did find that if I unplug the C connector at the ECU I hear the fuel pump kick on and my hondata lights up. I cannot start the car because of all the sensor that connect to the C connector but at least I know that is the issue. I now have to go through each wire and figure this all out. Recently I just removed and replaced my transmission so I am wondering if that had anything to do with it. Anyone know what might be causing no power to ECU only when the C connector is connected? Thanks for your time!

P.S. ALL dashboard lights come on when key is on and stay there. No check engine light flashing or going out once test is complete. All the lights stay on as long as the key is in on position.

Last edited by Kryptic1333; Jun 23, 2020 at 12:49 PM. Reason: Solved issue
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Old Jun 23, 2020 | 04:40 AM
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Default Re: 91 crx p28 hondata ecu no power - main relay good!

Clean and tighten the G3 transmission and G101 thermostat housing grounds.

Also carefully inspect the C connector pins and the corresponding pins in the conversion harness.
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Old Jun 23, 2020 | 12:49 PM
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Default Re: 91 crx p28 hondata ecu no power - main relay good!

Thanks for the response. It ended up being the TPS wire had a short and was shorting the ecu. As soon as I pulled the c connector while the power was on my fuel pump primed. Pulled every pin until I found the one that shorted it out and it was the TPS.
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Old Jun 23, 2020 | 12:58 PM
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Default Re: 91 crx p28 hondata ecu no power - main relay good!

Nice work!
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